The present invention relates to water-soluble polymers and compositions thereof, such water-soluble polymers and compositions thereof useful, e.g., in processes for selective separation of metal ions from aqueous streams, and processes for the selective separation of metals from solid matrixes.
Water-soluble polymers are well known for the retention or recovery of certain metal ions from solutions under certain conditions, e.g., certain pH conditions (see, e.g., Pure and Applied Chemistry, Vol. 52, pp. 1883-1905 (1980), Talanta, vol. 36, No. 8, pp. 861-863 (1989), and U.S. Pat. No. 4,741,831). Additionally, higher molecular weight varieties of the water-soluble polymers such as polyethyleneimine have been used as coatings on, e.g. silica gel, for separation and recovery of metal ions. However, the selectivity of the polymer for target metals due to competition from competing or interfering ions within solutions can present unique challenges.
It is an object of the present invention to provide novel water-soluble polymers.
It is a further object of the invention to provide compositions of water-soluble polymers having defined molecular weight ranges.
Still another object of the present invention is to provide compositions of water-soluble polymers including at least two different water-soluble polymers, the different water-soluble polymers differing in functionality, molecular weight range or both.
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention provides a water soluble polymer of the formula 
wherein X1, X2, and X3 in each unit of the polymer is a group independently selected from a substituent selected from H, C(O)CH2CH(SH)COOH,
xe2x80x83xe2x80x94(CH2)mYZp
where when m is an integer selected from 0, 2, 3, and 4, Y is selected from Cxe2x95x90O, Pxe2x95x90O, Cxe2x95x90S, SO2, C(O)CH2C(O), and S, Z is selected from an amine, alkylamine, arylamine, hydroxyl, oxyalkyl, oxyaryl, hydroxylamine, alkylhydroxylamine, arylhydroxylamine, thiol, alkylthiol, alkyl, aryl, dimethylpyrazolone, methylphenylpyrazolone, dimethylpyrazol-thione, methylphenylpyrazol-thione, oxycrown ethers, azacrown ethers, thiocrown ethers, and H, and when m is 1, Y is selected from Cxe2x95x90O, Cxe2x95x90S, SO2, C(O)CH2C(O), and S, Z is selected from an amine, alkylamine, arylamine, oxyalkyl, oxyaryl, hydroxylamine, alkylhydroxylamine, arylhydroxylamine, thiol, alkylthiol, alkyl, aryl, dimethylpyrazolone, methylphenylpyrazolone, dimethylpyrazol-thione, methylphenylpyrazol-thione, oxycrown ethers, azacrown ethers, thiocrown ethers, and H, p is an integer from 1 to 2, and n is an integer between about 12 and 12,000; or 
where m is an integer from 0 to 6, Y is selected from Cxe2x95x90O, Pxe2x95x90O, and Cxe2x95x90S, R1 and R2 are selected from an amine, alkylamine, arylamine, hydroxyl, oxyalkyl, oxyaryl, hydroxylamine, alkylhydroxylamine, arylhydroxylamine, thiol, alkylthiol. alkyl. aryl and H, p is an integer from 1 to 2, and n is an integer between about 12 and 12,000 with the proviso that at least one of X1, X2, and X3 is not hydrogen; 
wherein X4 and X5 in each unit of the polymer is a group independently selected from a substituent selected from H, C(O)CH2CH(SH)COOH,
xe2x80x94(CH2)mYZp
where q is an integer from 0 to 4, and where when m is an integer selected from 0, 2, 3, and 4, Y is selected from Cxe2x95x90O, Pxe2x95x90O, Cxe2x95x90S, SO2, C(O)CH2C(O), and S, Z is selected from an amine, alkylamine, arylamine, hydroxyl, oxyalkyl, oxyaryl, hydroxylamine, alkylhydroxylamine, arylhydroxylamine, thiol, alkylthiol, alkyl, aryl, dimethylpyrazolone, methylphenylpyrazolone, dimethylpyrazol-thione, methylphenylpyrazol-thione, oxycrown ethers, azacrown ethers, thiocrown ethers, and H, and when m is 1, Y is selected from Cxe2x95x90O, Cxe2x95x90S, SO2, C(O)CH2C(O), and S, Z is selected from an amine, alkylamine, arylamine, oxyalkyl, oxyaryl, hydroxylamine, alkylhydroxylamine, arylhydroxylamine, thiol, alkylthiol, alkyl, aryl, dimethylpyrazolone, methylphenylpyrazolone, dimethylpyrazol-thione, methylphenylpyrazol-thione, oxycrown ethers, azacrown ethers, thiocrown ethers, and H, p is an integer from 1 to 2, and n is an integer between about 24 and 24,000 with the proviso that at least one of X4 and X5 is not hydrogen; 
wherein X6 in each unit of the polymer is a group independently selected from a substituent selected from C(O)CH2CH(SH)COOH,
xe2x80x94(CH2)mYZp
where m is an integer selected from 0, 2, 3, and 4, Y is selected from Cxe2x95x90O, Pxe2x95x90O, Cxe2x95x90S, SO2, C(O)CH2C(O), and S, Z is selected from an amine, alkylamine, arylamine, hydroxyl, oxyalkyl, oxyaryl, hydroxylamine, alkylhydroxylamine, arylhydroxylamine, thiol, alkylthiol, alkyl, aryl, dimethylpyrazolone, methylphenylpyrazolone, dimethylpyrazol-thione, methylphenylpyrazol-thione, oxycrown ethers, azacrown ethers, thiocrown ethers, and H, and when m is 1, Y is selected from Cxe2x95x90O, Cxe2x95x90S, SO2, C(O)CH2C(O), and S, Z is selected from an amine, alkylamine, arylamine, oxyalkyl, oxyaryl, hydroxylamine, alkylhydroxylamine, arylhydroxylamine, thiol, alkylthiol, alkyl, aryl, dimethylpyrazolone, methylphenylpyrazolone, dimethylpyrazol-thione, methylphenylpyrazol-thione, oxycrown ethers, azacrown ethers, thiocrown ethers, and H, p is an integer from 1 to 2, and n is an integer between about 24 and 24,000;
xe2x80x94(CHX7xe2x80x94CH2)nxe2x80x94(CH2xe2x80x94CX8X9)mxe2x80x94xe2x80x83xe2x80x83(iv)
wherein X7 and X8, and X9 in each unit of the polymer is a group independently selected from a substituent selected from C(O)CH2CH(SH)COOH,
xe2x80x94(CH2)mYZp
where m is an integer selected from 0, 2, 3, and 4, Y is selected from Cxe2x95x90O, Pxe2x95x90O, Cxe2x95x90S, SO2, C(O)CH2C(O), and S, Z is selected from an amine, alkylamine, arylamine, hydroxyl, oxyalkyl, oxyaryl, hydroxylamine, alkylhydroxylamine, arylhydroxylamine, thiol, alkylthiol, alkyl, aryl, dimethylpyrazolone, methylphenylpyrazolone, dimethylpyrazol-thione, methylphenylpyrazol-thione, oxycrown ethers, azacrown ethers, thiocrown ethers, and H, and when m is 1, Y is selected from Cxe2x95x90O, Cxe2x95x90S, SO2, C(O)CH2C(O), and S, Z is selected from an amine, alkylamine, arylamine, oxyalkyl, oxyaryl, hydroxylamine, alkylhydroxylamine, arylhydroxylamine, thiol, alkylthiol, alkyl, aryl, dimethylpyrazolone, methylphenylpyrazolone, dimethylpyrazol-thione, methylphenylpyrazol-thione, oxycrown ethers, azacrown ethers, thiocrown ethers, and H, p is an integer from 1 to 2, and n is an integer between about 12 and 12,000, or 
wherein X10 and X11 in each unit of the polymer are a thiolactum or are a group independently selected from a substituent selected from C(O)CH2CH(SH)COOH, and
xe2x80x94(CH2)mYZp
where m is an integer from 0 to 4, Y is selected from Cxe2x95x90O, Pxe2x95x90O, Cxe2x95x90S, SO2, C(O)CH2C(O), and S; Z is selected from an amine, alkylamine, arylamine, hydroxyl, oxyalkyl, oxyaryl, hydroxylamine, alkylhydroxylamine, arylhydroxylamine, thiol, alkylthiol, alkyl, aryl, dimethylpyrazolone, methylphenylpyrazolone, dimethylpyrazol-thione, methylphenylpyrazol-thione, oxycrown ethers, azacrown ethers, thiocrown ethers, and H, p is an integer from 1 to 2, and n is an integer between about 24 and 24,000.
The present invention also provides a water soluble polymer of the formula 
wherein X1, X2, and X3 in each unit of the polymer is a group independently selected from a substituent selected from H, C(O)CH2CH(SH)COOH,
xe2x80x94(CH2)mYZp
where m is an integer from 0 to 4, Y is selected from Cxe2x95x90O, Pxe2x95x90O, Cxe2x95x90S, SO2, C(O)CH2C(O), and S, Z is selected from an amine, alkylamine, arylamine, hydroxyl, oxyalkyl, oxyaryl, hydroxylamine, alkylhydroxylamine, arylhydroxylamine, thiol, alkylthiol, alkyl, aryl, dimethylpyrazolone, methylphenylpyrazolone, dimethylpyrazol-thione, methylphenylpyrazol-thione, oxycrown ethers, azacrown ethers, thiocrown ethers, and H, p is an integer from 1 to 2, and n is an integer between about 12 and 12,000; 
where m is an integer from 0 to 6, Y is selected from Cxe2x95x90O, Pxe2x95x90O, and Cxe2x95x90S, R1 and R2 are selected from an amine, alkylamine, arylamine, hydroxyl, oxyalkyl, oxyaryl, hydroxylamine, alkylhydroxylamine, arylhydroxylamine, thiol, alkylthiol, alkyl, aryl, and H, p is an integer from 1 to 2, and n is an integer between about 12 and 12,000; 
wherein X4 and X5 in each unit of the polymer is a group independently selected from a substituent selected from H, C(O)CH2CH(SH)COOH,
xe2x80x94(CH2)mYZp
where q is an integer from 0 to 4, m is an integer from 0 to 4, Y is selected from Cxe2x95x90O, Pxe2x95x90O, Cxe2x95x90S, SO2, C(O)CH2C(O), and S, Z is selected from an amine, alkylamine, arylamine, hydroxyl, oxyalkyl, oxyaryl, hydroxylamine, alkylhydroxylamine, arylhydroxylamine, thiol, alkylthiol, alkyl, aryl, dimethylpyrazolone, methylphenylpyrazolone, dimethylpyrazol-thione, methylphenylpyrazol-thione, oxycrown ethers, azacrown ethers, thiocrown ethers, and H, p is an integer from 1 to 2, and n is an integer between about 24 and 24,000; 
wherein X6 in each unit of the polymer is a group independently selected from a substituent selected from C(O)CH2CH(SH)COOH,
xe2x80x94(CH2)mYZp
where m is an integer from 0 to 4, Y is selected from Cxe2x95x90O, Pxe2x95x90O, Cxe2x95x90S, SO2, C(O)CH2C(O), and S; Z is selected from an amine, alkylamine, arylamine, hydroxyl, oxyalkyl, oxyaryl, hydroxylamine, alkylhydroxylamine, arylhydroxylamine, thiol, alkylthiol, alkyl, aryl, dimethylpyrazolone, methylphenylpyrazolone, dimethylpyrazol-thione, methylphenylpyrazol-thione, oxycrown ethers, azacrown ethers, thiocrown ethers, and H, p is an integer from 1 to 2, and n is an integer between about 24 and 24,000;
xe2x80x94(CHX7xe2x80x94CH2)nxe2x80x94(CH2xe2x80x94CX8X9)mxe2x80x94xe2x80x83xe2x80x83(iv)
wherein X7, X8, and X9 in each unit of the polymer is a group independently selected from a substituent selected from C(O)CH2CH(SH)COOH,
xe2x80x94(CH2)mYZp
where m is an integer from 0 to 4, Y is selected from Cxe2x95x90O, Pxe2x95x90O, Cxe2x95x90S, SO2, C(O)CH2C(O), and S, Z is selected from an amine, alkylamine, arylamine, hydroxyl, oxyalkyl, oxyaryl, hydroxylamine, alkylhydroxylamine, arylhydroxylamine, thiol, alkylthiol, alkyl, aryl, dimethylpyrazolone, methylphenylpyrazolone, dimethylpyrazol-thione, methylphenylpyrazol-thione, oxycrown ethers, azacrown ethers, thiocrown ethers, and H, p is an integer from 1 to 2, and n is an integer between about 12 and 12,000; or 
wherein X10 and X11 in each unit of the polymer are a thiolactum or are a group independently selected from a substituent selected from C(O)CH2CH(SH)COOH, and
xe2x80x94(CH2)mYZp
where m is an integer from 0 to 4, Y is selected from Cxe2x95x90O, Pxe2x95x90O, Cxe2x95x90S, SO2, C(O)CH2C(O), and S; Z is selected from an amine, alkylamine, arylamine, hydroxyl, oxyalkyl, oxyaryl, hydroxylamine, alkylhydroxylamine, arylhydroxylamine, thiol, alkylthiol, alkyl, aryl, dimethylpyrazolone, methylphenylpyrazolone, dimethylpyrazol-thione, methylphenylpyrazol-thione, oxycrown ethers, azacrown ethers, thiocrown ethers, and H, p is an integer from 1 to 2, and n is an integer between about 24 and 24,000, said water-soluble polymer having a molecular weight of greater than about 10,000 and further characterized as essentially free of molecular weights less than about 10,000.
In one embodiment of the present invention, a water-soluble polymer is provided having nitrogen-, oxygen- or sulfur-containing groups capable of binding selected metal ions, said water-soluble polymer having a molecular weight of greater than about 30,000 and characterized as essentially free of molecular weights less than about 30,000.
In another embodiment of the invention, the water-soluble polymer includes functionalization from the group of amino groups, carboxylic acid groups, phosphonic acid groups, phosphonic ester groups, acylpyrazolone groups, hydroxamic acid groups, aza crown ether groups, oxy crown ethers groups, guanidinium groups, amide groups, ester groups, aminodicarboxylic groups, permethylated polvinylpyridine groups, permethylated amine groups, mercaptosuccinic acid groups, alkyl thiol groups, and N-alkylthiourea groups.
The present invention is concerned with water-soluble polymers, such water-soluble polymers useful, e.g., in the separation of various metals, e.g., toxic metals and/or precious and/or nuisance metals from aqueous streams.
The water-soluble polymers useful in practicing the present invention are synthetic water-soluble polymers, i.e., they are not naturally occurring water-soluble polymers such as starch, cellulose, and the like and do not involve modified naturally occurring water-soluble polymers. The water-soluble polymers used in the present invention generally include a nitrogen-, oxygen-, or sulfur-containing group. Exemplary of the water-soluble polymers used in the present invention are polyalkyleneimines such as polyethyleneimine and modified polyalkyleneimines, i.e., polyalkyleneimines such as polyethyleneimine where the water-soluble polymer includes functionalization selected from the group consisting of carboxylic acid groups, ester groups, amide groups, hydroxamic acid groups, phosphonic acid groups, phosphonic ester groups, acylpyrazolone groups, aza-crown ether groups, oxy-crown ether groups, guanidinium groups, thiolactam groups, catechol groups, mercaptosuccinic acid groups, alkyl thiol groups, and N-alkylthiourea groups. In addition to polyethyleneimine as the basic structure of many of the water-soluble polymers, other water-soluble polymer structures with nitrogen-containing groups such as poly(vinylamine), polyvinylpyridine, poly(acrylamide), and poly(allylamine), can be used. Also, water-soluble polymers structures with oxygen-containing groups such as poly(vinylalcohol) or oxygen- and nitrogen-containing groups such as polyvinylpyrrolidone can be used. The amine backbones can also be permethylated to give permethylpolyethyleneimine, permethylated polyvinylpyridine, permethylated polyallylamine, or permethylated polyvinylamine. Water-soluble polymers can be constructed from vinyl monomer polymerization reactions to give a number of pendent groups, copolymer of acrylamide and bis-phosphonic esters and acids. Water-soluble polymers with metal binding properties can be obtained from ring-opening reactions, e.g., the treatment of polypyrrolidone with base or hydroxylamine.
Exemplary of suitable functionalized water-soluble polymers are the reaction product of polyethyleneimine and an arylalkylhaloacetylpyrazolones such as phenylmethylchloroacetylpyrazolone or dimethylchloroacetylpyrazolone to yield a phenylmethylacetylpyrazolone-substituted or dimethylacetylpyrazolone-substituted polyethyleneimine, the reaction product of polyethyleneimine (polyallylamine, polyvinylamine) and a halocarboxylic acid such as bromoacetic acid or chloroacetic acid to yield an amino-carboxylate-substituted polyethyleneimine (polyallylamine, polyvinylamine), the reaction product of polyethyleneimine (polyvinylamine) and phosphorous acid and formaldehyde to give a phosphonic acid substituted polyethyleneimine (polyvinylamine), the reaction of polyethyleneimine and a monohydroxamic acid of succinic acid to give a hydroxamic acid substituted polyethyleneimine, the reaction of polyethyleneimine with acrylamide or ethylacrylate to give an ester or amide substituted polyethyleneimine, the reaction of vinylalcohol with a crown alcohol to give an oxycrown substituted vinylalcohol, the permethylation of polyvinylpyridine or polyethyleneimine or polyvinylamine or polyallylamine to give the respective permethylated polymers, the ring opening of polypyrrolidone with hydroxylamine to give the hydroxamic acid polymer, the copolymerization of a beta-bisphosphonic acid or ester with acrylamide to give a copolymer, the reaction of polyethyleneimine with a bisphosphonic acid or ester to give bisphosphonic acid or ester polyethyleneimine, and the reaction product of polyethyleneimine and a haloacetylaza crown material such as a chloroacetylaza crown ether to yield an aza crown ether-substituted polyethyleneimine.
When the polyethyleneimine is functionalized, care must be taken to control the level of functionalization as solubility problems at certain pH values can exist depending upon the type of functional groups and backbone used. The water-soluble polymers used in the present process preferably maintains their water solubility over the entire pH range of, e.g., pH 1 to 14. Preferably, any polyethyleneimine used in the present invention includes primary, secondary and tertiary amines. Bisfunctionalization can be realized for primary nitrogens allowing for multidentate character of some of the chelating groups. The polyethyleneimine is a branched polymer, giving it a globular nature and high charge density which partly accounts for its uniqueness in the polyamine family of polymers. This highly branched character also allows for better chelating site interactions with metal ions within the polymer. Other polyamines, i.e., polyvinylamine and polyallylamine, can be used as backbones, and are composed of all primary nitrogens, but they are linear polymers and if over functionalized can lead to insolubility in different pH ranges.
The use of prepurified (sized) polymer in the functionalization can be preferred in the process. Use of pre-purified polymer, e.g., polyethyleneimine, has the advantage that reagents used in subsequent functionalization steps are not lost on low molecular weight polyethyleneimine that will be lost in subsequent purification of the functionalized polymers. Further, it gives an extra margin of assurity that there will be no polymer leakage during the use of the polymers in any ultrafiltration process.
Conditions in the preparation of the water-soluble polymers can be important to assure that there is no detectable leakage through an ultrafiltration membrane during some subsequent processes. Several factors are important in aiding the presizing of the water-soluble polymers; the polymer concentration, the pH value, and the ionic strength at which the polymers are presized are all important. Because water-soluble polymers can aggregate in solution and because the polymers can expand or contract in size, conditions that effects these tendencies should be controlled. For example, it is known that polyethyleneimine can change it average size by 60% between a basic and acidic solution (larger in the acidic solution and smaller in basic). Thus, polyethyleneimine should be prepurified at the pH where its size is smallest to further assure the smaller fragments are remover from the larger fragments (at a pH of about 10-11). Other polymers because of either their neutral, anionic, or cationic nature will have different optimum pH values for prepurifying depending upon the pH that gives the smallest polymeric volume in solution. The ionic strength of a solution can also effect the polymeric volume in solution similarly to pH effects. If polymer concentration are too high in solution they will aggregate, again effecting the potential ability of obtaining polymers that are not going to leak through the membranes during any ultrafiltration process.
The prior art in the preparation of polyethyleneimine or other water-soluble polymers for use in metal separations has been quite vague in how it is prepared and treated for use in ultrafiltration techniques.
The present process to purify polyethyleneimine is unique in that the purification scheme does not clog the ultrafiltration membranes. In contrast, some polyethyleneimine manufacturers have been unable to develop a purification technique for sizing the polymer using ultrafiltration without severely and irreversibly clogging the membranes. Note that one other main use of polyethyleneimine is as an adhesive and polyethyleneimine is known to bind to many surfaces, especially cellulose and anionic surfaces. Polyethyleneimine has been reported to be fractionated by size using GPC (size exclusion chromatography), precipitation, and by exhaustive dialysis. Average molecular weight determinations were performed by osmometry, ultracentrifugation, viscometry, and light scattering techniques. Generally, the literature refers to determining the average molecular weight instead of producing fractions that do not pass an absolute molecular weight cutoff.
The water-soluble polymers of the present invention can be used in several potential compositions for selective separation of metal ions from aqueous streams or metals from solid matrixes. There can be a single polymer that will bind selectively with only one metal ion over all other ions and materials under the conditions of the process. Separation is achieved by binding that metal ion to the water-soluble polymer and then using a separation technique such as ultrafiltration to remove the water and other materials from the polymer. The polymer-bound metal ion is thus concentrated. The polymer-bound metal can be released from the polymer by a variety of processes as shown in the following equations:
M(P)+H+xe2x86x92HP+M+xe2x80x83xe2x80x83(eq. 1)
M(P)+Lxe2x86x92ML+(P)xe2x80x83xe2x80x83(eq. 2)
or
M(P)+exe2x88x92xe2x86x92Mx+(P)xe2x80x83xe2x80x83(eq. 3)
where M is the metal ion, (P) is the water-soluble polymer, L is a competing complexant. H+ is a proton, x is the valent state of the metal, and exe2x88x92 is an electron for an oxidation change reaction. Where the metal is released by a proton (eq. 1) or by a competing molecular ligand (eq. 2), the polymer-free metal ion is recovered by a diafiltration process. In some instances, the metal ion may be so tightly bound to the polymer that it is more desirable to heat process the concentrate to destroy the polymer (incineration, hot acid digestion, smelting, etc.) and recover the metal. Optionally, for waste management purposes it may be desirable to solidify the polymer-bound metal, e.g., in a grout or cement material, such that it passes toxic leach tests (TCLP).
Another potential composition can include a single polymer that will bind with a combination of metal ions under the process conditions. Separation and selectivity is realized by binding that combination of metal ions then using a separation technique such as ultrafiltration to remove the water and other materials from the polymer-metal complexes. The polymer-bound metals can be selectively released from the polymer by a variety of processes as shown above in equations 1, 2, and 3. Where the selected metal is released by protons (eq. 1) or by a competing molecular ligand (eq. 2), the polymer-free metal ion can be recovered by a diafiltration process. Stripping is repeated until all the desired metals have been selectively recovered. Again in some instances, the metal ions may be so tightly bound to the polymer that it is more desirable to heat process the concentrate to destroy the polymer to recover the metals. Optionally, for waste management purposes it may be desirable to solidify the polymer-bound metal, e.g., in a grout or cement material, such that it passes toxic leach tests (TCLP).
Still another composition uses a polymer formulation (two or more polymers of same molecular weight range) blended in such a ratio and with such functionality to have the desired selectivity that binds a combination of metal ions under certain conditions of pH, counter ion, and/or ionic strength. Separation is achieved by binding the metal ions to the water-soluble polymers and then using a separation technique such as ultrafiltration to remove the water and other materials from the polymer. The mixed polymer-bound metals are thus concentrated and can be further purified by washing with a clean solution in a diafiltration process to remove any final impurities. The polymer-bound metals can be selectively released from the polymers by a variety of processes as shown in equations 1, 2, and/or 3. When the process uses equation 1 and/or 2, the water-soluble polymers may be selectively stripped of the respective metal or group of metals by, e.g., appropriate pH control into a range whereat one polymer is stripped of its particular metal while the second water-soluble polymer retains its particular metal as a water-soluble polymer-bound metal. The second and subsequent polymers can be stripped of the remaining metal ions as desired for the separation process and the regeneration of the polymers for further reuse in the separation process.
Still another composition uses a polymer formulation (two or more polymers of different molecular weight range) blended in such a ratio and with such functionality to have the desired selectivity that binds a combination of metal ions under certain conditions of pH, counter ion, and/or ionic strength. Separation is achieved by binding the metal ions to the water-soluble polymer and then using a separation technique such as ultrafiltration to remove the water and other materials from the polymer. The mixed polymer-bound metals are thus concentrated and can be further purified by washing with a clean solution in a diafiltration process to remove any final impurities. The polymer-bound metals can be selectively released from the polymers by a variety of processes as shown in equations 1, 2, and/or 3. When the process uses equation 1 and/or 2, the water-soluble polymers may be selectively stripped of the respective metal ions or group of metal ions by, e.g., appropriate pH control into a range whereat one polymer is stripped of its particular metal while the second water-soluble polymer retains its particular metal as a water-soluble polymer-bound metal. The second and subsequent polymers can be stripped of the remaining metal ions as desired for the separation process and the regeneration of the polymers for further reuse in the separation process. Alternatively, since the water-soluble polymers are of different size ranges, it is possible to remove the metal from one polymer by the equations 1 to 3, and to separate the smaller polymer containing one type of functionality from the larger polymer with a different type of functionality. One of the functionalities is chosen to bind the metal ion of interest so tightly that the polymer that contains that functionality and the bound metal ions can be size separated from the other size polymer(s).
Another composition can include a single polymer or formulation of polymers that will bind with a single metal ion or a combination of metal ions under the conditions of the method. Separation and selectivity is realized by binding that combination of metal ions to the water-soluble polymer or polymers, then using a single pass separation technique such as ultrafiltration to remove the water and other materials from the polymer-bound metals. The polymer-bound metals are further concentrated to dryness or near dryness onto a flat ultrafiltration membrane. The membrane is either dissolved or digested in appropriate medium or leached with an appropriate acid or ligand to totally recover the metals that were on the membrane. The recovered solution which constitutes a concentrate of selected metal ions from the original solution can then be analyzed using appropriate analytical instrument or wet chemistry techniques.
Another composition can include a single polymer or formulation of polymers that will bind with a single metal ion or a combination of metal ions under the conditions of the process. Separation is achieved by binding the selected metal ions to the water-soluble polymer or polymers and then using a separation technique such as biphasic liquid-liquid extraction to remove other materials and unbound metal ions from the aqueous polymer solution. The metals that are unbound to the polymer and go into the organic or second phase are separated from the polymer-containing aqueous phase by standard phase separation techniques, e.g., mixer settlers, liquid extraction membranes, or centrifugal contactors, etc. The metals can be back-extracted from the second phase to another aqueous phase for recovery purposes. The polymer can be regenerated from the aqueous stream by first concentration ultrafiltration followed by diafiltration. This process can be reversed by back extracting the metal ion of interest from a biphasic system using aqueous solutions of the water-soluble polymer.
Generally, the concentration of the water-soluble polymer in metals separation is from about 0.001 weight to volume percent to about 25 weight to volume percent of final mixed solution, more preferably from about 0.001 weight to volume percent to about 5 weight to volume percent of final solution. It is sufficient and in some cases desirable to have at least just enough polymer in solution such that the molar ratio of polymer to metal ions in solution is one. Using high concentrations of the water-soluble polymer can most often result in a lower flux or flow during an ultrafiltration stage. The use of high polymer concentration can also cause an aggregation effect where no or little metal ion binding occurs to the polymer when the metal ion sees a high initial concentration of polymer. During the diafiltration stage the polymer and metal bound polymer concentration can often become quite high and in the case where the solution goes to near dryness it can approach 90% of the weight of the concentrate.
After the solution containing the water-soluble polymer is contacted with the aqueous solution for a sufficient period of time to form water-soluble polymer-metal complex, separation of the water-soluble polymer-metal complex is preferably accomplished by ultrafiltration. Ultrafiltration is a pressure driven separation occurring on a molecular scale. As a pressure gradient is applied to a process stream contacting the ultrafiltration membrane, liquid including small dissolved materials are forced through pores in the membrane while larger dissolved materials and the like are retained in the process stream. Pressure gradients can be created, as desired, from the use of vacuum systems, centrifugal force, mechanical pumping, and pressurized air and/or gas systems (e.g., nitrogen).
In the use of the present water-soluble polymers, an ultrafiltration unit can generally consist of hollow-fiber cartridges or membrane material having a 1,000 MWCO to 1,000,000 MWCO preferably 10,000 MWCO to 100,000 MWCO. Other membrane configurations such as spiral-wound modules, stirred cells (separated by a membrane), thin-channel devices, centrifuge units (separated by a membrane) and the like may also be used although hollow-fiber cartridges are generally preferred for the continuous/semicontinuous process filtration units. For analytical applications for preconcentration purposes stirred cells and centrifuge ultrafiltration units are preferred. Small hollow-fiber cartridges also can be used for continuous preconcentration for analytical applications. Among the useful ultrafiltration membranes are included cellulose acetate, polysulfone, and polyamide membranes such as polybenzamide, polybenzamnidazole, and polyurethane.
The use of ultrafiltration for separation is further described in Kirk Othmer: Encyclopedia of Polymer Science and Engineering, 2nd Ed., vol. 17, pp. 75-104, 1989, such description incorporated herein by reference.
Generally, the water-soluble polymers have molecular weights of from greater than 1,000 to about 1,000,000, and preferably from greater than 10,000 to 100,000. Above molecular weights of 1,000,000 some polymers tend to lose solubility, while polymers below molecular weight of about 1000, retention by suitable ultrafiltration membranes can present problems such as low flux rates.
The water-soluble polymers of the present invention can be provided with distinct preselected molecular weight ranges through purification or sizing. For example, by filtering polyethyleneimine through the particular size ultrafiltration membrane (e.g., UFP-10-C-5 available from AG Technologies, Corp. with available MWCO""s of 10,000, 30,000 and 100,000), polyethyleneimine can be provided with: (1) a molecular weight range of greater than about 10,000 and essentially free of molecular weights of less than about 10,000; (2) a molecular weight range of greater than about 30,000 and essentially free of molecular weights of less than about 30,000; (3) a molecular weight range of greater than about 100,000 and essentially free of molecular weights of less than about 100,000; (4) a molecular weight range of from about 10,000 to about 30,000 and essentially free of molecular weights of less than about 10,000 and greater than about 30,000; (5) a molecular weight range of from about 10,000 to about 100,000 and essentially free of molecular weights of less than about 10,000 and greater than about 100,000; and, (6) a molecular weight range of from about 30,000 to about 100,000 and essentially free of molecular weights of less than about 30,000 and greater than about 100,000. Other water-soluble polymers can be sized in a similar fashion. Other preselected ranges should become available as other membranes with other MWCO""s become available.
The water-soluble polymers can be used in the recovery of metal ions from aqueous streams as described by Smith et al., in U.S. patent application serial number 08/453,406, filed concurrently herewith, entitled xe2x80x9cWater-Soluble Polymers for Recovery of Metal Ions from Aqueous Streamsxe2x80x9d, can be used in the recovery of metals from solids as described by Smith et al., in U.S. patent application serial number 08/453,596, filed concurrently herewith, entitled xe2x80x9cWater-Soluble Polymers for Recovery of Metals from Solidsxe2x80x9d, and can be used for the displacement of cyanide ions from metal-cyanide complexes as described by Smith et al., in U.S. patent application serial number 08/453,597, filed concurrently herewith, entitled xe2x80x9cProcess for the Displacement of Cyanide Ions from Metal-Cyanide Complexesxe2x80x9d, such descriptions incorporated herein by reference.